This relates generally to imaging systems, and more particularly, to imaging systems with global shutter functionality.
Modern electronic devices such a cellular telephones, cameras, and computers often use digital image sensors. Imagers (i.e., image sensors) often include a two-dimensional array of image sensing pixels. Each pixel typically includes a photosensor such as a photodiode that receives incident photons (light) and converts the photons into electrical signals.
Conventional image sensors are fabricated on a semiconductor substrate using complementary metal-oxide-semiconductor (CMOS) technology or charge-coupled device (CCD) technology. In CMOS image sensors, a rolling shutter or a global shutter may be used. In a global shutter, every pixel in the image sensor may simultaneously capture an image, whereas in a rolling shutter each row of pixels may sequentially capture an image. In CMOS image sensors with a global shutter, a charge storage region is typically incorporated into each pixel to store charge from the photodiode until read out. However, these pixels may not be able to acquire high dynamic range (HDR) images, which limits the functionality of the image sensor. Additionally, these pixels may not be able to acquire images using correlated double sampling (CDS) techniques. This may increase noise in the pixels and decrease the image quality of the image sensor.
It would therefore be desirable to be able to provide improved CMOS image sensors with global shutter functionality.